Photopolymerizable resin compositions for optical recording media and optical recording media

ABSTRACT

The present invention relates to photopolymerizable resin composition inducing substantially no chemical degradation in metals in tight contract with the resin. Further, the present invention relates to optical recording media using the photopolymerizable resins. In one embodiment, a photopolymerizable resin composition includes a photopolymerizable resin based on acrylic ester, and an additive based on at least one selected from the group consisting of benzotriazole and a derivative of benzotriazole, and a photointiator.

TECHNICAL FIELD

The present invention relates to photopolymerizable resins used inoptical recording media, particularly photopolymerizable resincompositions used for bonding two substrates.

BACKGROUND ART

Conventional media for reading or reading/writing memory data by usinglight include optical recording media such as compact disks and DVDs(Digital Versatile Discs).

As an example of these media, reference 100 in FIG. 4 represents anoptical recording medium used as a DVD, comprising first and secondsubstrates 111, 121, first and second reflective films 115, 125 and aresin layer 140.

First reflective film 115 is formed on a surface of first substrate 111,and resin layer 140 is provided in tight contact with the side of firstreflective film 115 opposite to first substrate 111. Second reflectivefilm 125 is provided in tight contact with the side of resin layer 140opposite to first reflective film 115, and second substrate 121 isprovided on the side of second reflective film 125 opposite to resinlayer 140.

Generally, resin layer 140 consists of a cured product of aphotopolymerizable resin such as epoxy acrylate, in which impure ionssuch as chlorine ion are liable to remain during its preparation processand any impure ions or water remaining in resin layer 140 may chemicallydegrade reflective films 115, 125 in tight contact with resin layer 140.

Especially, on reflective films consisting of a thin metal film based onsilver, chemical degradation such as oxidation or sulfurization isliable to be caused and degraded reflective films 115, 125 discolor tono longer serve as reflective films.

In order to prevent such chemical degradation, JPA No. 126370/1999describes a method for protecting reflective films from a resin layer byforming a protective film consisting of silicon dioxide or the like onthe surfaces of the reflective films and bringing the resin layer intotight contact with the surface of the protective film.

However, such a protective film had the disadvantage that a more complexprocess is required for manufacturing an optical recording medium andhigh costs are incurred.

The present invention was made to overcome the disadvantages of theprior art described above with the purpose of providing aphotopolymerizable resin composition suitable for a resin layer formedin tight contact with reflective films of optical recording media.

DISCLOSURE OF THE INVENTION

The present invention provides a photopolymerizable resin compositioncontaining a photopolymerizable resin based on an acrylic ester, anadditive based on either one or both of benzotriazole and abenzotriazole derivative, and a photoinitiator.

In the photopolymerizable resin composition of the present invention,the additive is contained at 0.01 parts by weight or more per 100 partsby weight of the total weight of the photopolymerizable resin and thephotoinitiator.

In the photopolymerizable resin composition of the present invention,the additive is contained at 0.05 parts by weight or more and 5 parts byweight or less per 100 parts by weight of the it's total weight of thephotopolymerizable resin and the photoinitiator.

In the photopolymerizable resin composition of the present invention,the additive is based on either one or both of 1,2,3-benzotriazole and aderivative of 1,2,3-benzotriazole.

The present invention also provides an optical recording mediumcomprising a substrate, a first reflective film provided on thesubstrate and a resin layer provided in tight contact with the firstreflective film wherein the resin layer consists of a photopolymerizableresin composition containing a photopolymerizable resin based on anacrylic ester, an additive based on either one or both of benzotriazoleand a derivative of benzotriazole, and a photoinitiator.

In the optical recording medium of the present invention, a secondreflective film is in tight contact with the surface of the resin layeropposite to the side with which the first resin film is in tightcontact.

In the optical recording medium of the present invention, the firstreflective film is based on silver.

In the optical recording medium of the present invention, the resinlayer has a thickness in the range of 1 μm or more and 200 μm or less.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a, 1 b, 1 c, and 1 d are diagrams for illustrating a process formanufacturing a first example of an optical recording medium of thepresent invention.

FIGS. 2 a, 2 b, 2 c, and 2 d are diagrams for illustrating a secondexample of an optical recording medium of the present invention togetherwith the manufacturing process.

FIG. 3 is a diagram for illustrating a third example of an opticalrecording medium of the present invention.

FIG. 4 is a diagram for illustrating an optical recording medium of theprior art.

Various references in the drawings represent the following elements: 1,50, 70, optical recording medium; 11, 21, 51, 71, substrate (first orsecond substrate); 15, 25, 55, 75, reflective film (first or secondreflective film); 35, 65, 76, resin layer (protective film).

THE MOST PREFERRED EMBODIMENTS OF THE INVENTION

Photopolymerizable resin compositions of the present invention containan additive such as benzotriazole or a benzotriazole derivative servingto protect metals against chemical degradation, so that no chemicaldegradation occurs in reflective films consisting of a chemicallyunstable metal such as silver even when a resin layer consisting of aphotopolymerizable resin composition of the present invention isdirectly brought into tight contact with the reflective films.

If either one of first or second reflective film of optical recordingmedia of the present invention consists of a transmissive material, evena laser beam emitted from the side of the substrate having thetransmissive reflective film can be directed to the other reflectivefilm to read data because the laser beam can pass through thetransmissive reflective film to reach the other reflective film.

Such photopolymerizable resin compositions can be applied on areflective film on a surface of a substrate and then cured by UVirradiation to form a protective film of an optical recording mediumsuch as a compact disk.

Photopolymerizable resin compositions and optical recording media of thepresent invention are explained in detail below.

Initially, a photopolymerizable resin was prepared by adding 24 parts byweight each of acrylic esters, ie., dicyclopentadiene diacrylate (soldunder the name of “R684” by Nippon Kayaku Co., Ltd.), EO-modifiedtrimethylolpropane triacrylate (sold under the name of “SR351” bySartomer Company Inc.) and tripropylene glycol diacrylate (sold underthe name of “SR306” by Sartomer Company Inc.) to 24 parts by weight ofan urethane acrylate oligomer (sold under the name of “CN983” bySartomer Company Inc.).

To this photopolymerizable resin were added and mixed 4 parts by weightof a photoinitiator (sold under the name of “Irgacure 184” by CibaSpecialty Chemicals K.K.) and 0.5 parts by weight of an additive1,2,3-benzotriazole to prepare a photopolymerizable resin composition ofExample 1.

References 11, 21 in FIGS. 1(a), 1(b) represent first and secondsubstrates, respectively, used in an optical recording medium of thepresent invention.

Pits 12, 22 are formed on one side of first and second substrates 11,21, respectively, and first and second reflective films 15, 25 areformed by sputtering on the surfaces of these pits 12, 22, respectively.

First and second reflective films 15, 25 have a thickness smaller thanthe height of pits 12, 22 so that the pattern of pits 12, 22 isreflected on reflective films 15, 25.

First substrate 11 here consists of a transmissive polycarbonate resinand first reflective film 15 formed on first substrate 11 consists of asemi-transmissive metal film based on silver. Second reflective film 25formed on second substrate 21 consists of a metal film based onaluminum.

In order to prepare an optical recording medium of the present inventionusing first and second substrates 11, 21 as described above and thephotopolymerizable resin composition of Example 1 as described above,the photopolymerizable resin composition is first dropped on the surfaceof first reflective film 15 formed on first substrate 11, then secondreflective film 25 formed on second substrate 21 is brought into tightcontact with the surface of the first reflective film 15, and then thephotopolymerizable resin composition is uniformly spread over thesurface of first reflective film 15 by spin coating to prepare a resincomposition layer consisting of the photopolymerizable resin compositionbetween first and second reflective films 15, 25.

Reference 30 in FIG. 1(c) represents the resin composition layer, whichis provided in tight contact with the surfaces of first and secondreflective films 15, 25.

Then, the surface of first substrate 11 in this state is irradiated withUV rays. When UV rays pass through transparent first substrate 11 toreach resin composition layer 30, the photopolymerizable resincomposition forming resin composition layer 30 is polymerized by UV raysso that resin composition layer 30 is cured while resin compositionlayer 30 is in tight contact with first and second reflective films 15,25. Thus, first and second reflective films 15, 25 on the surfaces offirst and second substrates 11, 21 are bonded together by cured resincomposition layer 30.

Reference 1 in FIG. 1(d) represents an optical recording medium formedby bonding first and second reflective films 15, 25.

A resin layer 35 formed of cured resin composition layer 30 is providedbetween first and second substrates 11, 21 of optical recording medium1, and resin layer 35 is in tight contact with first and secondreflective films 15, 25 formed on the surfaces of first and secondsubstrates 11, 21.

Data in optical recording medium 1 is recorded as pits 12, 22 on thesurfaces of first and second substrates 11, 21 and read by directing alaser beam 45 at a predetermined wavelength (a red laser beam at awavelength of 650 nm or a blue laser beam at a wavelength of 440 nm) tothe surface of first substrate 11 of optical recording medium 1 (FIG.1(d)).

When laser beam 45 is condensed on the interface 13 between firstsubstrate 11 and first reflective film 15 (a first data reading face),the beam reflected by reflective film 15 varies in intensity with thepattern of pits 12 on first substrate 11.

Thus, data recorded as pits 12 on the surface of first substrate 11 canbe read by detecting variations in the intensity of the reflected beam.

On the other hand, data recorded as pits 22 on the surface of secondsubstrate 21 can also be read by directing laser beam 45 to the surfaceof first substrate 11 of optical recording medium 1, as described forfirst data reading face 13.

Laser beam 45 partially passes through first reflective film 15 formedon the surface of first substrate 11 because first reflective film 15 issuitably transmissive to laser beams at a predetermined range ofwavelength.

After having passed through first substrate 11 and first reflective film15, laser beam 45 reaches second reflective film 25 without beingrefracted or scattered in resin layer 35 because resin layer 35 providedin tight contact with first reflective film 15 has a refractive indexnearly equal to that of first substrate 11.

The data can also be read from the interface 23 between secondreflective film 25 and resin layer 35 (a second data reading face)bycondensing the laser beam on second data reading face 23 and detectingvaries in the intensity of the beam reflected by reflective film 25because the pattern of pits 22 on the surface of second substrate 21 isreflected on second reflective film 25 (single-sided reproduction).

This optical recording medium 1 was subjected to a “hightemperature/high humidity test” below.

<High Temperature/High Humidity test>

Optical recording medium 1 formed by the process above was left for 50hours under the conditions of 85° C., relative humidity 95% (hightemperature/high humidity storage), after which the state of firstreflective film 15 of optical recording medium 1 was observed. Theresults are shown in Table 1 below in the column of “state of reflectivefilm/general aspect” in which “∘” means that first reflective film 15generally maintains the same silver color as before hightemperature/high humidity storage and “x” means that it generallychanges into a dark color. Separately, discolored black spots localizedon first reflective film 15 are counted and the number of discoloredspots is shown in Table 1 below in the column of “state of reflectivefilm/number of discolored spots”.

The results of “total evaluation” in the “high temperature /highhumidity test” are also shown in Table 1 below in which “∘” means thatfirst reflective film 15 contains less than 50 discolored spots, “Δ”means that first reflective film 15 contains 50 or more discolored spotsbut generally maintains the silver color, and “x” means that firstreflective film 15 contains 50 or more discolored spots and changes intoblack.

TABLE 1 Types of additives and high temperature/high humidity testresults State of reflective film Number of Total Chemical Generaldisclolored evalu- Protective additive formula aspect spots ationExample 1 Benzotriazole Formula (1) ◯ 0 ◯ Example 2 MethylbenzotriazoleFormula (2) ◯ 0 ◯ Example 3 1-(N,N-Bis(2-ethylhexyl) Formula (3) ◯ 5 ◯aminomethyl)benzotriazole Example 4 Carboxybenzotriazole Formula (4) ◯ 3◯ Example 5 3-(N-Salicyloyl) Formula (5) X 10 ◯ amino-1,2,4-triazoleComparative 2-Mercaptobenzothiazole Formula (6) X 50 or more X Example 1Comparative 2-Methylimidazole Formula (7) X 50 or more X Example 2Comparative 2-Methyl-4- Formula (8) X 50 or more X Example 3ethylimidazole Comparative 2-Undecylimidazole Formula (9) X 50 or more XExample 4 Comparative 2-Heptadecylimidazole Formula (10) X 50 or more XExample 5 Comparative 2-Phenylimidazole Formula (11) ◯ 50 or more ΔExample 6 Comparative 1-Cyanoethyl-2- Formula (12) X 50 or more XExample 7 methylimidazole Comparative 1-Cyanoethyl-2-ethyl-4- Formula(13) X 50 or more X Example 8 methylimidazole Comparative1-Cyanoethyl-2- Formula (14) X 50 or more X Example 9 phenylimidazoleComparative 1-Cyanoethyl-2- Formula (15) X 50 or more X Example 10undecylimidazole Comparative — — ◯ 50 or more Δ Example 11

EXAMPLES 2-5

Methylbenzotriazole was used as an additive in place of1,2,3-benzotriazole used in Example 1 and mixed with thephotopolymerizable resin and photoinitiator used in Example 1 in thesame proportions as in Example 1 to prepare a photopolymerizable resincomposition of Example 2.

The photopolymerizable resin composition of Example 2 was used incombination with first and second substrates 11, 21 in the state shownin FIGS. 1(a), (b) to prepare an optical recording medium 1 of Example 2by the same process as in Example 1.

Similarly to Example 2,1-(N,N-bis(2-ethylhexyl)aminomethyl)benzotriazole, carboxybenzotriazoleand 3-(N-salicyloyl)amino-1,2,4-triazole were used as additives in placeof 1,2,3-benzotriazole used in Example 1 to prepare photopolymerizableresin compositions of Examples 3-5 and optical recording media 1 ofExamples 3-5 using them.

These optical recording media 1 of Examples 2-5 were subjected to the“high temperature/high humidity test” under the same conditions as inExample 1 and the test results are shown in Table 1 above.

The additives used in Examples 2-4 are 1,2,3-benzotriazole derivativesand the additive used in Example 5 is a 1,2,4-benzotriazole derivative.The compounds forming the additives used in Examples 2-5 (formula(2)-(5)) and the additive used in Example 1 (formula (1)) arerepresented by the chemical formulae below.

COMPARATIVE EXAMPLES 1-11

Similarly to Example 2, 2-mercaptobenzothiazole, 2-methylimidazole,2-methyl-4-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole,2-phenylimidazole, 1-cyanoethyl-2-methylimidazole,1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazoleand 1-cyanoethyl-2-undecylimidazole were used as additives in place of1,2,3-benzotriazole used in Example 1 to prepare photopolymerizableresin compositions of Comparative examples 1-10 and optical recordingmedia 1 of Comparative examples 1-10 using them.

Separately, the photopolymerizable resin and photoinitiator used inExample 1 were mixed in the same proportions as in Example 1 with noadditives to prepare a photopolymerizable resin composition ofComparative example 11 and an optical recording medium of Comparativeexample 11.

These optical recording media of Comparative examples 1-11 weresubjected to the “high temperature/high humidity test” under the sameconditions as in Example 1 and the test results are shown in Table 1above. The additives used in Comparative examples 1-10 are representedby chemical formulae (6)-(15) below.

The additive used in Comparative example 1 is a derivative of thiazoleand the additives used in Comparative examples 2-10 are derivatives ofimidazole.

As shown in Table 1 above, less discolored spots occurred in opticalrecording media 1 using the photopolymerizable resin compositions ofExamples 1-5 than using the photopolymerizable resin compositions ofComparative examples 1-10 in the “high temperature/high humidity test”.Especially, very few discolored spots occurred in Examples 1-4 using1,2,3-benzotriazole or a derivative thereof as an additive.

EXAMPLES 6-12

The photopolymerizable resin and photoinitiator used in Example 1 weremixed in the same proportions as in Example 1 and combined with theadditive used in Example 1 in varying amounts (parts by weight) as shownin Table 2 below to prepare photopolymerizable resin compositions ofExamples 6-12.

The photopolymerizable resin compositions of Examples 6-12 were used toprepare optical recording media 1 of Examples 6-12 by the same processas in Example 1. These optical recording media 1 were subjected to the“high temperature/high humidity test” under the same conditions as inExample 1. The results are shown in Table 2 below.

TABLE 2 Amounts of additive and high temperature/ high humidity testresults State of reflective film Number of Total Amount of additiveGeneral disclolored evalu- (parts by weight) aspect spots ation Example6 10 X 0 Δ Example 7 8 X 0 Δ Example 8 5 ◯ 0 ◯ Example 9 3 ◯ 0 ◯ Example10 1 ◯ 0 ◯ Example 1 0.5 ◯ 0 ◯ Example 11 0.05 ◯ 2 ◯ Example 12 0.01 ◯11 ◯ Comparative None ◯ 50 or more Δ Example 11

In Table 2 above, the results of the “high temperature/high humiditytest” on Comparative example 11 described above are also shown.

As shown in Table 2 above, less local discolored spots occurred inoptical recording media 1 using the photopolymerizable resincompositions of Examples 6-12 as compared with Comparative example 11.

Especially, very few discolored spots were observed when thephotopolymerizable resin compositions of Example 1 and 8-11 were used inwhich the amount of the additive is in the range of 0.05 parts by weightor more and 5 parts by weight or less per 100 parts by weight of thetotal weight of the photopolymerizable resin and the photoinitiator.

Example 12 showed eleven local discolored spots but no generaldiscoloration, confirming that an anti-degradation effect is obtained sofar as the amount of the additive is 0.01 parts by weight or more per100 parts by weight of the total weight of the photopolymerizable resinand the photoinitiator.

Another example of an optical recording medium of the present inventionis described in detail below.

Initially, a photopolymerizable resin was prepared by mixing 32 parts byweight each of acrylic esters, ie, dicyclopentadiene diacrylate,trimethylolpropane triacrylate and tripropylene glycol diacrylate.

To this photopolymerizable resin were added and mixed 4 parts by weightof a photoinitiator (sold under the name of “Irgacure 184” by CibaSpecialty Chemicals K.K.) and 0.5 parts by weight of an additive1,2,3-benzotriazole to prepare a photopolymerizable resin composition ofExample 13.

Reference 51 in FIG. 2(a) represents a transparent substrate. Substrate51 used here consists of a polycarbonate resin. A pigment layer 56 isformed on the surface of substrate 51, and a reflective film 55 isformed on the surface of pigment layer 56. Reflective film 55 hereconsists of a metal thin film based on silver.

In order to prepare an optical recording medium of the present inventionusing substrate 51 in this state, the photopolymerizable resincomposition of Example 13 above is first dropped on the surface ofreflective film 55 on substrate 51 to form a photopolymerizable resincomposition layer by spin coating, and then the photopolymerizable resincomposition is cured by UV irradiation.

Reference 50 in FIG. 2(b) represents an optical recording medium formedby curing the photopolymerizable resin composition layer, and aprotective film (resin layer) 65 consisting of the curedphotopolymerizable resin composition layer is provided on the surface ofreflective film 55 of optical recording medium 50.

This type of optical recording medium 50 is a so-called CD-R (CompactDisk-Recordable), in which data are recorded by directing a laser beamto the surface of substrate 51 of optical recording medium 50 andcondensing the laser beam at a desired spot on pigment layer 56 on theopposite side of substrate 51. The spot on pigment layer 56 at which thelaser beam is condensed is heated and discolored (baking).

FIG. 2(c) shows pigment layer 56 discolored in a desired pattern, andreference 52 in FIG. 2(c) represents a discolored spot in pigment layer56. Data are recorded as a pattern of discolored spots 52 in opticalrecording medium 50.

Recorded data are read by directing a laser beam 45 at a predeterminedwavelength to the surface of substrate 51 of optical recording medium 50(FIG. 2(d)) and condensing it on the interface 53 between pigment layer56 on the opposite side of substrate 51 and reflective film 55 (datareading face).

The data recorded as a pattern of discolored spots 52 can be read bydetecting variations in the intensity of the reflected laser beambecause the laser beam is reflected at a different reflectance indiscolored spots 52 in pigment layer 56 from the remaining area.

Predetermined data were recorded in optical recording medium 50 preparedby the process described above using a data recorder sold under the nameof “CRW4260tx” by YAMAHA. Optical recording medium 50 in this state wassubjected to a “C1 error rate test” shown below to determine the C1error rate.

<C1 Error Rate Test>

A CD-ROM analyzer sold under the name of “DR-3755” by KENWOOD TMI wasused to detect the C1 error on optical recording medium 50, and the C1error rate was determined.

Separately, optical recording medium 50 was stored for 200 hours underhigh temperature/high humidity conditions (80° C., relative humidity85%) and optical recording medium 50 in this state was measured for C1error rate value by the same procedure as for the initial value. Theresults are shown as the value after high temperature/high humidity testin Table 3 below.

TABLE 3 Compositions of photocurable resins and C1 error rate testresults C1 error rate After high Composition of temperature/photocurable resin Initial value high humidity test Example 13Photocurable resin 2.0 × 10⁻⁴ 2.2 × 10⁻⁴ composition/photoinitiator/additive Comparative Photocurable resin 2.0 × 10⁻⁴ 4.6 ×10⁻² composition/ Example 12 photoinitiator

COMPARATIVE EXAMPLE 12

The same photopolymerizable resin and photoinitiator as used in Example13 were mixed in the same proportions as in Example 13 with no additivesto prepare a photopolymerizable resin composition of Comparative example12.

Using this photopolymerizable resin composition, a protective film wasformed by the same process as in Example 13 on the reflective film onthe surface of the substrate in the state shown in FIG. 2(a) to preparean optical recording medium. This optical recording medium was used todetect the C1 error before and after high temperature/high humidity testunder the same conditions as in Example 13, and the C1 error rate wasdetermined. The results are shown in Table 3 above.

As shown in Table 3 above, the C1 error rate value after hightemperature/high humidity test was lower in optical recording medium 50using the photopolymerizable resin composition of Example 13 than usingthe photopolymerizable resin composition of Comparative example 12. Itwas confirmed from these results that photopolymerizable resincompositions of the present invention can be used to obtain protectivefilm 60 having the high ability of protecting reflective film 55.

Although the foregoing description relates to the case in whichdicyclopentadiene diacrylate, trimethylolpropane triacrylate andtripropylene glycol diacrylate are used as acrylic ester components ofthe photopolymerizable resin, the present invention is not limitedthereto but various acrylates can be used.

Oligomers that can be used in combination with these acrylic esters arenot specifically limited, either. Photopolymerizable resin compositionsof the present invention may contain various agents such as surfacetension modifiers, silane coupling agents, water, etc.

Although Examples 1-12 above relates to examples of optical recordingmedia such as DVD in which either one of first or second reflective film15, 25 consists of a transmissive metal such as silver and one 11 offirst and second substrates 11, 21 on which transmissive reflective film15 is formed consists of a transparent polycarbonate resin, the presentinvention is not limited thereto.

For example, both of two reflective films may consist of anon-transparent metal such as aluminum. Data in such an opticalrecording medium can be read by separately directing a laser beam toboth sides of the optical recording medium (the surfaces of first andsecond substrates) and reading the reflected beam (double-sidedreproduction). In this case, both first and second substrates shouldconsist of a transparent material.

Although reflective films 15, 25, 55 consisting of a metal such assilver or aluminum were provided in tight contact with substrates 11,21, 51 or resin layers 35, 65 in Examples 1-12 above, the presentinvention is not limited thereto. For example, a dielectric layerconsisting of silicon nitride or the like may be formed on at least oneof reflective films.

Although Example 13 above relates to an optical recording medium 50(CD-R) having pigment layer 56 formed on the surface of substrate 51,the present invention is not limited thereto.

Reference 70 in FIG. 3 represents a read-only optical recording medium(CD-ROM: Compact Disk Read Only Memory). This optical recording medium70 comprises a substrate 71, a reflective film 75 provided on thesurface of substrate 71 and a protective film 76 provided on the surfaceof reflective film 75, and protective film 76 consists of a curedproduct of a photopolymerizable resin composition of the presentinvention. Similarly to optical recording medium 10 shown in FIG. 1(c),data are recorded as a pattern of pits on the surface of substrate 71 ofoptical recording medium 70 shown in FIG. 3.

Rewritable optical recording media (CD-RW: Compact Disk Rewritable)having a phase change recording layer in place of pigment layer 56 shownin FIGS. 2(c), 2(d) are also included in the present invention. In theseoptical recording media (CD-ROM, CD-RW), the reflective films can beprevented from chemical degradation by using a photopolymerizable resincomposition of the present invention to form a protective film.

Photopolymerizable resin compositions of the present invention can beused to obtain an optical recording medium with high resistance tomoisture and heat even when silver is used as the metal for reflectivefilms.

1. A photopolymerizable resin composition, comprising: aphotopolymerizable resin based on acrylic ester; an additive based on atleast one selected from the group consisting of 1,2,3-benzotriazole,methylbenzotriazole, 1-(N,N-bis(2-ethylhexyl)aminomethyl)benzotriazole,carboxybenzotriazole, and 3-(N-salicycloyl)amino-1,2,4-triazole; and aphotoinitiator.
 2. The photopolymerizable resin composition of claim 1,wherein the additive comprises at least 0.01 parts by weight per 100parts by weight of a total weight of the photopolymerizable resin andthe photoinitiator.
 3. The photopolymerizable resin composition of claim1, wherein the additive comprises between 0.05 parts by weight and 5parts by weight per 100 parts by weight of a total weight of thephotopolymerizable resin and the photoinitiator.
 4. An optical recordingmedium, comprising: a substrate; a first reflective film provided on thesubstrate; and a resin layer provided in tight contact with the firstreflective film, wherein the resin layer consists of aphotopolymerizable resin composition comprising a photopolymerizableresin based on acrylic ester, an additive based on 1,2,3-benzotriazoleand a photoinitiator, wherein the first reflective film is based onsilver.
 5. The optical recording medium of claim 4, further comprising asecond reflective film in tight contact with a surface of the resinlayer opposite to a side with which the first reflective film is intight contact.
 6. The optical recording medium of claim 4, wherein theresin layer has a thickness in a range between 1 μm and 200 μm.
 7. Theoptical recording medium of claim 5, wherein the resin layer has athickness in a range between 1 μm and 200 μm.
 8. An optical recordingmedium, comprising: a substrate; a first reflective film provided on thesubstrate; and a resin layer provided in tight contact with the firstreflective film, wherein the resin layer consists of aphotopolymerizable resin composition comprising a photopolymerizableresin based on acrylic ester, an additive based on a derivative of1,2,3-benzotriazole, and a photoinitiator, wherein the first reflectivefilm is based on silver.
 9. The optical recording medium of claim 8,further comprising a second reflective film in tight contact with asurface of the resin layer opposite to a side with which the firstreflective film is in tight contact.
 10. The optical recording medium ofclaim 8, wherein the resin layer has a thickness in a range between 1 μmand 200 μm.
 11. The optical recording medium of claim 9, wherein theresin layer has a thickness in a range between 1 μm and 200 μm.
 12. Anoptical recording medium, comprising: a substrate; a first reflectivefilm provided on the substrate; and a resin layer provided in tightcontact with the first reflective film; wherein the resin layer consistsof a photopolymerizable resin composition comprising aphotopolymerizable resin based on acrylic ester, an additive based on aderivative of 1,2,4-benzotriazole, and a photoinitiator, wherein thefirst reflective film is based on silver.
 13. The optical recordingmedium of claim 12, further comprising a second reflective film in tightcontact with a surface of the resin layer opposite to a side with whichthe first reflective film is in tight contact.
 14. The optical recordingmedium of claim 12, wherein the resin layer has a thickness in a rangebetween 1 μm and 200 μm.
 15. The optical recording medium of claim 13,wherein the resin layer has a thickness in a range between 1 μm and 200μm.